Cracks in cement-based mortar, putty and cracks are common problems. In many years of research and practice, the author believes that the cracks of plastering mortar, putty on exterior wall and the causes of cracks mainly come from "internal" and "external" aspects.

　　1、“内因”方面

　　1. Internal Causes

　　“内因”方面主要是由于一些抹面砂浆、腻子产品的干缩性大、干缩快，产生较大内应力破坏了砂浆结构而引起裂纹的，裂纹的表现一般呈不规则的龟裂状，也就是常说的龟裂纹，主要是一些生产厂家对原材料性质、作用与技术原理上了解不充分，所用原材料不符合要求，配方不科学，导致产品质量不稳定、抗裂性能差，施工后不久就出现大面积龟裂、空鼓、脱落问题。

　　"Internal cause" is mainly due to the drying shrinkage of some plastered mortar and putty products, which causes cracks due to the destruction of mortar structure by large internal stress. The cracks generally show irregular tortoise cracks, that is to say, tortoise cracks. The main reason is that some manufacturers do not fully understand the nature, function and technical principles of raw materials, and the raw materials used do not conform to each other. According to the requirements, unscientific formulation leads to unstable product quality and poor crack resistance. Large area cracking, empty drum and shedding problems occur shortly after construction.

　　水泥砂浆的强度、防裂效果都与水有重要关系，水泥的水化与凝结硬化是一个渐进式、连续性过程，先水化，后凝结，凝结硬化结果如何，要取决于水化条件，水化的越充分、水养护的越好、水养护的时间越长，强度就会越高，收缩性就越小，防裂效果就越好；水泥的水化与凝结硬化速度受环境温度的影响也是明显的，即环境温度高，水化与硬化速度就快，环境温度低时，水泥的水化与凝结硬化的速度相应就慢些。凡是早干、早硬、早强的水泥砂浆，因保水不好、自养护能力差，会产生收缩过快、收缩力过强、容易产生大面积龟裂。在研究与实践中，早干、早硬、早强的水泥砂浆的后期强度及稳定性、抗裂性均比晚干、晚硬、晚强的水泥砂浆要差，这也是水泥作为无机水硬性胶凝材料的特殊性所决定的。

　　The strength and anti-cracking effect of cement mortar are closely related to water. The hydration and condensation hardening of cement are a gradual and continuous process. The results of hydration first, then, and condensation hardening depend on the hydration conditions. The more fully hydration, the better water curing and the longer water curing time, the higher the strength, the smaller the shrinkage and the better the anti-cracking effect. The rate of cement hydration and setting hardening is also obviously affected by environmental temperature, that is, the rate of hydration and hardening is faster when the environmental temperature is high, and the rate of cement hydration and setting hardening is slower when the environmental temperature is low. The cement mortar with early drying, early hardening and early strength will shrink too fast, shrink too strongly and easily crack in large area due to poor water retention and poor self-curing ability. In research and practice, the late strength, stability and crack resistance of early-drying, early-hardening and early-strength cement mortar are worse than those of late-drying, late-hardening and late-strength cement mortar, which is also determined by the particularity of cement as inorganic hydraulically cementing material.

　　龟裂纹的产生，主要与水泥有关，不论是什么类型的水泥，都存在干缩问题，从试验情况看，硫铝酸盐水泥、白水泥等水泥品种的后期强度及稳定性、抗裂性就不及普通硅酸盐水泥好，主要是这些产品本身的收缩性大，干缩较快、收缩力较强、容易产生龟裂纹。普通硅酸盐水泥在我国建筑工程上的应用很普遍，有好几十年的历史，它的性能是很好的，经研究与试验，只要水化充分、水养护条件较好，几年后、甚至十年后其强度还会有所提高。目前，聚合物砂浆、水泥类腻子仍以普通硅酸盐水泥为主，所使用的型号为32.5R或42.5R，其在聚合物抹面砂浆、水泥类腻子产品中的配方量一定要掌握好。

　　The crack of tortoise is mainly related to cement. No matter what type of cement, there is drying shrinkage problem. From the test results, the strength, stability and crack resistance of sulphoaluminate cement, white cement and other cement varieties are not as good as ordinary Portland cement. The main reason is that these products have larger shrinkage, faster drying shrinkage, stronger shrinkage force and are prone to tortoise crack. Ordinary Portland Cement is widely used in China's construction engineering. It has a history of several decades. Its performance is very good. Through research and test, as long as the hydration is sufficient and the water maintenance condition is good, its strength will be improved in a few years or even ten years. At present, polymer mortar and cement putty are still based on ordinary Portland cement. The type used is 32.5R or 42.5R. The formulation of polymer plastering mortar and cement putty products must be well controlled.

　　2、“外因”方面

　　“外因”方面，主要是施工工艺、地基和自然环境引起的。通常情况下，建筑设计施工不科学和不合理，地基沉降、偏离，施工时一次性抹的太厚、施工前基底已经出现明显裂缝、地震、大的风压产生的应力、施工后连续性的高温干旱天气等，都会引起裂缝的产生，裂缝、裂纹的表现一般以裂缝为多，形状有横线式、竖线式或呈不规则式。

　　The external causes are mainly caused by construction technology, foundation and natural environment. Usually, unscientific and unreasonable architectural design and construction, settlement and deviation of foundation, excessive thickness of one-time plastering during construction, obvious cracks in basement before construction, earthquake, stress caused by large wind pressure, continuous high temperature and drought weather after construction, etc., will cause cracks. Cracks and cracks are generally manifested in the form of horizontal lines and vertical lines. Type or irregular.

　　3、水泥砂浆与水泥基腻子的裂纹裂缝的另一个特征是：无论抹多厚或抹多薄，其裂纹裂缝都是从面一直裂到底，这也是建筑物发生渗漏水的根本原因。裂纹裂缝有大小之分，大的裂纹裂缝可以很容易看到，小的裂纹裂缝肉眼不一定看得出来，但只要往干燥的墙面上泼洒水，微细的裂纹裂缝就能清楚地看到。

　　3. Another characteristic of crack in cement mortar and cement-based putty is that no matter how thick or thin it is, the crack always cracks from the surface to the end, which is also the most fundamental reason for water leakage in buildings. Cracks can be divided into different sizes. Large cracks can be easily seen. Small cracks may not be visible to the naked eye, but as long as water is sprinkled on the drying wall, fine cracks can be clearly seen.

　　4、只要出现裂纹、裂缝，基本上没有什么可靠的材料和技术手段可以彻底修复，其结果会给建筑装饰、装修、防水工程以及今后的维修工作造成极大的困难，这是因为外墙裂缝、裂纹在随着外部所处的环境条件(地基沉降、地震等)和较大温差、干湿度变化的同时，其缝隙大小、形状也在随之不停地变化，即冬季低温与夏季高温时缝隙大小会变化，就是在同一季节下雨天与晴朗天，缝隙大小也会发生变化，总之每天24小时都处于变化之中，这也是裂缝、裂纹在屋面、墙面、地下防水工程及维修实践中，也是令人头痛的事，经常是修好后，不到一年甚至是几个月内，又开始渗漏。只要没有任何裂纹裂缝，一般情况下建筑物是不会发生渗漏水的，凡了解水泥水池的人，就明白只要没有任何裂纹裂缝，水泥水池是不会发生渗漏水的。

　　4. As long as cracks and cracks occur, there is basically no reliable material and technical means to repair them thoroughly. The result will cause great difficulties in building decoration, decoration, waterproof engineering and future maintenance. This is because cracks and cracks in external walls are accompanied by environmental conditions (foundation settlement, earthquakes, etc.) and at the same time with large temperature difference and dry humidity change. The size and shape of cracks are constantly changing, that is, the size of cracks will change when the temperature is low in winter and high in summer. Even in rainy and sunny days in the same season, the size of cracks will change 24 hours a day. This is also the most headache of cracks and cracks in roof, wall, underground waterproof Engineering and maintenance practice. Often it starts to leak again in less than a year or even a few months after repair. As long as there are no cracks, the building will not leak water in general. Anyone who knows the cement pool knows that as long as there are no cracks, the cement pool will not leak water.